NEW YORK (NYTimes) - Released in June, Katy Perry's fourth major label album, Witness, has been her least commercially successful and her most artistically confused.

Take Bon Appetit, the album's second single, a disco-esque club song featuring the rat-tat-tat Atlanta rap trio Migos. Perry is somewhere in there, singing, but her voice is the least essential part of the song. And in the video, she's manhandled like dough by a gaggle of chefs, then covered in vegetables before getting dumped in a cauldron and basted.

It's all quite dizzying, not the sort of spectacle that's easily replicable onstage. But when Perry came to Madison Square Garden on Monday night as part of her Witness tour, she gamely tried, finishing her performance of the song - pleasantly reduced to a hard synthesizer line with her vocals faint in the background - draped on an oversized leaf, with dancers dousing her in powder with huge salt and pepper shakers.

It was game, wacky, mildly over-compensatory. She is the only performer in pop history with three separate singles achieving diamond certification from the Recording Industry Association of America. But she understands that extra-musical assistance is what makes the music really sing.

That's because Perry is a pop star without ideology - not a provocateur, or a ruthless power-grabber, or a vocal powerhouse. She perceives pop as ecstatic experience, and an end unto itself. More Carol Burnett than Madonna, she's sturdy in her goofiness, and fluent in froth and frill.

Which explains why the most exemplary elements of this exuberantly distracting concert were those executed in service of making her seem bigger, bolder, more creatively thoughtful and dynamic.

At this carnival, she wasn't quite a ringleader, but more like a wide-eyed enthusiast let loose among a cornucopia of playthings.

The set design was impeccable, turning the arena into a galaxy, with planets dangling from the sky, during Thinking Of You, and she mounted on a sleek pink motorcycle for Hey Hey Hey. During the craven-as-ever I Kissed A Girl, Perry's first hit single, she was hoisted up into a waiting pair of pillowy red lips and then chomped down on repeatedly. She performed Swish Swish from atop, and then inside, a huge basketball hoop.

And the costumes on her many dancers were consistently fresh, from the Ettore Sottsass-inspired chess pieces during Teenage Dream to the bodysuits draped in green, orange and pink hair on Part Of Me. At times, two performers controlled towering bodies - flamingos in one section, and Max Headroom-like dystopic figurines in another - with a set of puppetry sticks.

At one point, she was joined by Left Shark, a character drawn from her 2015 Super Bowl performance, a reminder that Perry has been deep-diving into plasticity for some time now. (You could buy your own Left Shark costume at the merchandise kiosk for US$160 (S$218).

Amid all this, Perry was as confident and adept onstage as she's ever been, but in service of new material that's among her weakest, including ponderous songs like Tsunami and Power. Often, her live vocals were low in the mix, but at times, they were surprisingly strong, like on older songs, from the era when guitar featured more prominently in her work, including Hot N Cold, or Thinking Of You, which she delivered with an acoustic guitar while seated on a planet soaring above the crowd.

Given that bombastic vocals are not Perry's strongest gift, it's striking that she closed her show with Roar and Firework, two big-throated anthems, songs that take her out of her fun house and plant her firmly atop an aspirational mountain.

They were well-executed, but Perry was plainly more at ease when she could carry out her Everywoman approach to megafame, like when she invited an audience member - "a dad!" she screamed - to play basketball with her, or when she made a plea for peace and tolerance and then brought a young girl onstage for a hug and a chat. What did the girl want to do when she grew up, Perry wondered. To take pictures of animals in their natural habitat, the girl replied. Someone should have handed her a camera.

The Straits Times

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